Although attention has a central role in age-related decline in cognitive abilities, a barrier to progress, in the cognitive neuroscience of aging, is that little is known regarding the age-related differences in brain structure and function that are relevant for attention. This research addresses the issue of age- related differences in visual attention, from two complementary perspectives: age-related differences in the neural mechanisms associated with visual attention, and the relative influence of different aspects of brain structure and function on age-related differences in measures of visual attention. The theoretical framework for this research proposes that age-related differences in behavioral (attentional) performance represent the combined influences of individual differences in several variables: a) the magnitude of task-related regional activation; b) the functional connectivity (FC) associated with the temporal coherence of the fMRI signal; and c) the integrity of white matter pathways. Five experiments are planned that will examine age-related differences in different aspects of visual search and discrimination. Each experiment will contain separate cohorts of healthy, community-dwelling adults from three age groups: 20-39, 40-59, and 60-79 years of age. Across the experiments, the research will address three specific aims. The first aim is to investigate age-related differences in the magnitude and FC of task-related activation. The hypothesis is that age-related differences in activation, within different components of the frontoparietal network, will vary in relation to: the requirement to combine visual features (Experiments 1-2), the selection of relevant features and resistance to attentional capture (Experiments 3-4), and the control of competing responses (Experiment 5). The second aim is to investigate age-related differences in resting-state (intrinsic) FC, in terms of the temporal coherence of the spontaneous, low-frequency fluctuations in the fMRI signal. Four intrinsic FC networks (default mode; dorsal and ventral attentional; visual sensory) will be investigated, with the hypothesis that age-related decline in intrinsic FC will vary in magnitude across the networks. The third aim is to identify the relative influence of task-related activation, FC, and white matter integrity (from DTI), as mediators of age-related differences in cognitive performance. The hypothesis is that although all of the variables will mediate the relation between age and visual attention, individual differences in white matter integrity have a more direct influence on intrinsic FC than on task-related FC. If the research aims are achieved, the results would impact the cognitive neuroscience of aging, by providing a new integration of neural and behavioral data relevant to visual attention. These data, from healthy individuals, is a necessary foundation for the diagnosis and treatment of cognitive impairments.